Set ComboBox selected value from form.load()

I've got a form inside a LayoutDialog. This form loads its data dynamically when a row in a grid is double clicked. Most of it works great, but one field, a ComboBox, does not select its appropriate value automatically.

The ComboBox also loads its values dynamically via JSON. What do I need to do to select the appropriate value in the ComboBox when the form loads data?

The "Name" and "url" are my textfields names. the country is the combo box name. Please note that in order to display a new value in the combo box you must send a value that exists in the combo box and only then it will be able to show the responded value.

setValue( String/String[] value ) : Ext.form.field.FieldSets the specified value(s) into the field. For each value, if a record is found in the store that matches based on the valueField, then that record's displayField will be displayed in the field. If no match is found, and the valueNotFoundText config option is defined, then that will be displayed as the default field text. Otherwise a blank value will be shown, although the value will still be set.